Furnace



Dec. 17, 1935.

P. H. KOCH 2,024,232

FURNACE Filed Aug. 3, 1952 4 Sheets-Sheet 1 II as ATTORNEY Dec. 17, 1.935.

P. H. KOCH FURNACE Filed Aug. 3, 1932 Fi f2 4 Sheets-Sheet v 2 Fig. 3

2 [6 INVENTOR 3 7 J da! Jfffociz 3/ 5v R i.

ATTORNEY P. H. KOCH Dec. 17, 1935.

FURNACE Filed Aug. 3, 1952 4 Sheets-Sheet 3 ATTORNEY P. H. KOCH Dec. 17, 1935.

FURNACE Filed Aug. 3, 1952 4 Sheets-Sheet 4 ,lf fqla Jul an/Z 01 Paul H [Cock Patented Dec. 11, 1935 UNITED STATES FURNACE imnxoeawutaaa,

mam

N.J.,asllgnorto".l'he

(Jammy, Bayonne, N. 1., acorporation New Jersey Application August 3,

25mins.

Myinvention relates to a furnace and is applicable to a boiler furnace having water-cooled walls and a water-cooled floor.

One object of the invention is the provision of supporting means for the walls and floor of a furnace. A further object is the provision of such means in a form which will restrain the furnace against all motion at one point and permit expansion of the furnace away from that point while fully supporting the same. Still a further object is the provision of a furnace construction wherein the walls are held firmly against the floor to prevent leakage into or out of the furnace. Other objects will appear upon consideration of the present specification.

The invention is shown by way of illustration in the accompanying drawings wherein- Figure l is a vertical longitudinal midsection through a furnace and part of a boiler above. said furnace, a part of the furnace being shown in elevation, all constructed in accordance with the invention,

Fig.2isapartialhorizontalseetiononthe line 11-11 of Figure 1,.

Fig. 3 is a partial elevation of the furnace as viewed from the right in Figure 1 partly shown in section along the line IIIIII of Figure 1,

Fig. 4 is an enlarged sectional view showing the detailed construction in the lower righthand portion of Fig. 3, the section being taken on the line IVIV of Fig. 5,

Fig. 5 is a view of the construction illustrated in Fig. 4 as indicated by the line V-V thereon,

Fig. 6 is a plan view of the construction illustrated in Fig. 7 along the line VIVI,

Fig. 7 is an enlarged sectional view showing the detailed construction of the elements illustrated in the lower right-hand portion of Figure 1,

Fig. 8 is a fragmentary front elevation of the wall support and restraining means,

Fig. 9 is a fragmentary side sectional view of the wall support,

Fig. 10 is a detail section taken on the line ||l of Fig. 9, and

Fig. 11 is a diagrammatic view illustrating the direction of movement of the walls and floor of the furnace due to expansion and contraction thereof.

In the construction which is shown in the drawings for purposes of illustration, there is a furnace ll having a front wall II, a rear wall l2 and sidewalls l3-l3. The wallsareof theusual water tube and block construction having lower 1932, Serial No. 627,316

headers ll, l5, and lt-lt, respectively, at the lower ends of the tubes therein.

A floor I1 is provided at the bottom of the furnace, this floor comprising a series of parallel tubes ll each connected to the front lower header I4, and each being reduced in outer section near its other end to pass between the wall tubes in the rear wall l2, beyond which they are connected into a box header It. The tubes ll preferably slope downwardly toward the rear of the furnace to promote circulation through them and to facilitate collection of slag on the floor, the box header I! being at the downtake end of their connections with the boiler. Blocks 2. overlie the floor tubes l8 and provide the surface of the 5 furnace floor. Clamps 2| may be provided on the opposite sides of the tubes l8 partly surrounding the same and connected in the usual, or any convenient manner, with the blocks to hold the latter in place. Ledge blocks 22 are 20 preferably provided along the corners formed between the walls and the floor to reduce any possible thrust of growing slag upon the walls.

Lower tubes 23 of a boiler above the furnace III are illustrated in Figure 1. For simplicity, however, steam and water connections between the boiler and the wall and floor tubes are not illustrated, such connections being well known in the art.

Pulverized fuel burners 24 and a secondary airbox 25 are shown in connection with the front wail of the furnace, and a slag tap opening 26 is illustrated in one of the side walls of the furnace as in Fig. 2.

In accordance with my invention I anchor one of the walls, for example, the front wall II, at one point so as to prevent movement of the wall at that-point and I support the remaining portions of such one wall, the other walls, and the floor so that they are permitted to move toward and away from such point of anchorage incident to expansion and contraction. I also lash or connect the upright walls II, I! and I: to the edges of the floor or bottom wall ll so that spreading or movement of the floor and walls due to changes of temperature or any other strains or forces, will not result in the leakage of slag.

The supporting structure for the front wall II is shown in Fig. 1, and more clearly in Fig. 8, as being a plurality of spaced saddles 21 fixed to the header II and resting on shoes 21a, the latter being rigidly connected to a pair of supporting channels 28, which form a part of the main supporting structure for the furnace. As shown inFig,8, oneofthesaddles 2'Iisrlgidly flxedbyu bolts to its respective shoe 21a and thereby forms the means for anchoring the front wall at one point. The remaining saddles 21 are freeto slide on the upper surface of their respective shoes, thus providing for movement of the wall II toward and away from the point of anchorage due to expansion and contraction. The front wall is further restrained by means of I-beams I la which are a part of the fixed external supporting structure of the furnace and prevents outward movement of the wall I I at the elevation at which such beam is located.

If desired, the structure shown for slidably supporting the remaining parts of wall Ii may be replaced by roller supports such as are disclosed in Fig. 1 in connection with the rear wall I! and in Fig. 3 in connection with the side wall l3. These roller supports comprise saddles 29 constructed slightly different from the saddles 21. The saddles 29 are fixed to their respective headers IE or I6 and rest upon rolling elements, here shown as balls 30, which in turn are carried by a supporting bed plate 29a. While I have shown balls 30 as the means providing the rolling support, it is to be understood that other means may be resorted to without departing from the spirit of the present invention, for example, I might choose to use cylindrically-shaped rollers instead of the balls. It will thus beseen that I have provided a slidable support for the rear wall [2 and side walls l3 as well as the unrestrained portions of the wall II.

The side walls may move outward or toward the point of anchorage with the outer extremities of wall II and, as stated, provision is made for movement of the side walls due to expansion and contraction thereof. However, movement of the side walls due to their own expansion and contraction should not affect the front wall. To this end, I provide a guide construction 21b which 10- cates each header it at the end adjacent the wall i l with respect to the main furnace supporting structure. The guide constructions 21b permit movement of the wall H and the walls IS in directions parallel to the plane of wall I l and also permit movement of walls l3 due to expansion and contraction thereof, but the guide constructions prevent the latter movement of walls l3 from affecting front wall ii.

The different movements of the walls II, I! and I3 will be readily understood from an examination of Fig. 11, wherein I have indicated diagrammatically the furnace and by arrows the direction in which the walls and floor expand and contract with respect to the point to which the front wall II is anchored. The reference character A denotes the point of anchorage of wall II and the arrows parallel to the wall ll indicate the expansion and contraction of this wall due to changes in temperature within the furnace, or for any other causes incident to furnace operation. The guide constructions 211) are indicated and the arrows parallel to walls l3 indicate the direction of movement of these walls due to expansion and contraction, the arrows parallel to the wall I! indicate the directionof movement of this wall. The dotted lines indicate in an exaggerated way the position of the walls H, I! and I3 when fully expanded.

As the header It serves both the tubes forming the wall II and the tubes forming the bottom wall or floor H, the wall I1 is also anchored at one point and expands both longitudinally and transversely from this point. The floor is slidably supported, as will presently appear, and is connected or lashed at its edges to the walls I2 and I3 to prevent separation of the walls from the floor and consequent leakage of molten slag.

The floor I1 is slidably supported by shoes 3| which may be fixed to the floor by the same means as are provided for securing the blocks 30 and clamps 3| to the tubes. The bottom surfacecf the shoes 3| slidably engage I-beams 32, which are a part of the main furnace supporting structure. The bottom surface of the shoes 3| are preferably machined to facilitate sliding thereof on the I-beams.

Other forms of slidable support, both for the walls through their lower headers and for the floor, may be provided without departing from the spirit of the present invention. In any event, one wall of the furnace has one point flxed,and the entire furnace is slidably supported permitting expansion thereof in any direction away from and contraction toward the fixed point. The structural support whereby such motion of the walls and floor is permitted may be formed of rolling supports, as well as the illustrated supports which are shown to be in slidable contact.

Means is also provided for restraining or limiting movement of the rear wall and side walls of the furnace. This means is shown as comprising a plurality of vertically disposed buckstays 33 which are pivoted in their upper ends at intermediate points in the vertical extent of the:

adjacent walls. The buckstays 33 are pivoted as indicated at 34 to angle irons 35 carried by supporting I-beams 36, which together with a second I-beam 33a attached thereto, form a part of the main supporting structure for the furnace.

Buckstay clamps or blocks 31 are rigidly attached to the walls and are in sliding contact by a slot and washer connection with the interior face of the I-beams 35. This construction provides for movement in the plane of the wall, but prevents 33 are so arranged with respect to the lower portions of the side and rear walls and are so connected thereto as to stiffen the lower portions of such walls and at the same time permit movement of the lower portions of such walls and floor incident to expansion and contraction.

The walls I! and I3 are lashed or connected to the floor by means of tension members or tierods 39 which connect the lower ends of the pivoted buckstays to the floor, and the buckstays acting through the compression elements 38 transmit the tension forces set up by the tie-rods 39 into compression forces acting against the walls I! and I3.

The means for lashing the rear wall I2 to the floor I1 is clearly illustrated in Figs. 6 and 7.

Channels 40 are disposed transversely of and at each side of the lower and reduced ends of the floor tubes It. The channels engage at one side lugs Illa which are welded to the top and bottom sides of the tubes l8 and engage at the other side clamps b which serve to hold blocks ll and 32 on the wall tubes. The blocks 22 have been previously described as ledge blocks for closing the spaces between the wall tubes and for relieving thrust of the slag pool on the side and rear walls. The blocks I also close the spaces between the wall tubes. An angle plate He serves as a sealing means to aid in preventing leakage of slag. Bolts a connect the channels to the tubes and one end of the rods 3! is pivotally connected to the bolts, the other end of the rods pass between spaced channels 39a, the latter rigidly connecting the outer ends of buckstays 33 for movement in unison about their pivots. Nuts 42 on the threaded outer ends 43 of the rods 39 serve to tighten the connection with the channels 39a and buckstays 38. Thus the wall I! is firmly held against the floor I'I.

The manner of lashing or connecting the floor to the side walls It is illustrated in Figs. 4 and 5. The outer ends of the tie-rods are connected to the buckstays 33 and through the compression members or beams 38 to the wall I! in the same manner as was previously described. The inner ends of the tie-rods are connected to spaced channel sections 44 which are arranged above and below rounded extensions 46 of plate members 45. The plate members extend transversely of the tubes l8 and are secured to other plates 48 also extending transversely ofthe tubes l8. The plates 45 and I8 are secured to the floor by bolts 45a which also serve as the means for securing the blocks 20 and clamps 2| to the tubes. Plates l9 extend between the spaced plates 48 and are connected thereto by any suitable means, such for example, as welding as indicated at a. The rounded outer ends 48 of plates 45 are threaded and nuts 41 serve to connect the plates 45 to the channel sections It, and hence the floor to the tie-rods. It will thus be seen that the side walls I; are securely lashed to the floor-in the same manner as the rear wall is lashed to the fioor.

An additional feature of the construction is illustrated in Fig. 2 wherein the horizontal longitudinal members external to the furnace wall, are broken up, that is to say, a member does not extend continuously across the wall. Sliding contact between the wall and these members is provided in the same manner as has been described in connection with the blocks 31 and the I-beams 38. The purpose of such a construction is to allow for the fact that the wall being heated to a greater degree will expand to a larger extent than will these external members.

When the furnace here illustrated is actually built, it is found desirable to anticipate the expansion of the floor, and to deflect each wall inwardly toward its lower end. Thus, when the furnace is put into operation, and becomes heated, the floor expands and the lower ends of the walls are deflected outwardly. The wall then becomes straight. It is necessary, of course, to provide the proper initial clearances between adjacent wall ends in order that proper contact may be made between them when each wall becomes straight. It is also necessary to make appropriate adjustment of the nut 42 on the end of the tie-rod 39 in order that the pivoted buckstay 33 may be properly stressed.

It will be noted that in the present construction there is little relative movement between the I claim:

1. In a furnace, four walls, a flcor comprising water tubes surrounded by said walls and connected thereto, means for restraining one of said walls against all motion at one point therein,

' means providing slidable support for the rest of the restrained wa l, for said other walls, and for said floor, and means for exerting limited restraint upon the wall opposite said restrained wall. l0

2. In a furnace, four walls, a fioor comprising water tubes surrounded by said walls and connected thereto, a fixed support, a wall connection fixed to the support for restraining one of said walls against all motion at one point therein, means providing slidable support for the rest of the restrained wall, for said other walls, and for said fioor, a pivoted buckstay mounted for exerting limited restraint upon the wall opposite said restrained wall. connections between the buckstay and the fioor, and a wall stop carried by the buckstay and contacting with a wall.

3. In a furnace, walls, a floor comprising water tubes surrounded by said walls and connected thereto, means for restraining one of said walls 2 against all motion at one point therein, rolling elements providing support for the rest of the restrained wall, other rolling elements providing support for the other walls, and means providing slidablesupport for the fioor.

4. In a furnace, walls, a floor comprising water tubes surrounded by said walls and connected thereto, means for restraining one of said walls against all motion at one point therein, rolling elements providing support for the rest of the restrained wall, other rolling elements providing support for the other walls, and means providing slidable support for the floor, in combination with means for exerting limited restraint upon the wall opposite said restrained wall.

5. In a furnace, walls, a door comprising water tubes surrounded by said walls and connected thereto, a fixed support, a wall connection fixed to the support for restraining one of said walls against all motion at one point therein, rolling elements providing support for the rest of the restrained wall, other rolling elements providing support for the other walls, means providing slidable support for the floor, in combination with a pivoted buckstay mounted for exerting limited restraint upon the wall opposite said restrained wall, connections between the buckstay and the floor, and a wall stop carried by the buckstay and contactingwith a wall.

6. In a furnace, a front wall, a fixed support, a 5 wall connection fixed to the support for restraining said front wall against all motion at one point therein, a back wall opposite said front wall, side walls, rolling elements 'providing support for the unrestrained parts of said front wall, rolling elements providing support for said back wall and said side walls, pivoted buckstays mounted for exerting limited restraint upon said back walls and said side walls, connections between the buckstay and the floor, and a wall 5 stop carried by the buckstay and contacting with a wall.

7. In a furnace, a front wall, a fixed support,

a wall connection fixed to the support for restraining said front wall againstall motion at one point therein, a back wall opposite said front wall, side walls, a fioor surroimded by said walls, means providing slidable support for said fioor, rolling elements providing support for the unrestrained parts of said front wall, rolling elements providing support for said back wall and said side walls, pivoted buckstays mounted for exerting limited restraint upon said back wall and said side walls, connections between the buckstay and the fioor, and a wall stop carried by the buckstay and contacting with a wall.

8. In a furnace, a front wall, a fixed support, a wall connection fixed to the support for restraining said front wall against all motion at one pointtherein, a back wall opposite said front wall, side walls, a floor comprising water tubes surrounded by said walls and connected thereto, and means providing slidable support for said floor, in combination with rolling elements providing support for the unrestrained parts of said front wall, rolling elements providing support for said back wall and said side walls, pivoted buckstays mounted for exerting limited restraint upon said back wall and said side walls, connections between the buckstay and the floor, and a wall stop carried by the buckstay and contacting with a wall.

9. A slag tap furnace comprising, in combination, a floor including spaced cooling tubes and adapted to support a pool of slag deposited from the products of combustion, walls including spaced cooling tubes and extending to positions below the floor level, tension members connected to the floor tubes, buckstays pivoted at their upper ends at positions considerably above the furnace floor, means connecting the tension members and the buckstays, compression members interposed relative to the walls and the buckstays to press the walls against the marginal portions of the floor, a fixed support, a rigid connection between the support and one wall at one position along that wall, and supports for other parts of the last mentioned wall and the fioor permitting these parts to move toward or from the position of said connection with the fixed support.

10. A slag tap furnace, comprising, in combination, means for burning a slag producing fuel in the furnace, a floor constructed to sustain a pool of slag and including spaced cooling tubes, walls about the fioor and including spaced wall tubes, a fixed support, a rigid connection between the support and the floor and one wall of the furnace at one position, secondary wall supports providing for movement of the parts of that wall remote from said connection toward or away from said position, floor supports providing for movement of the floor toward or from said position, means connected to the floor tubes and contacting with another wall of the furnace to provide an increase or decrease in the cross section of the furnace near the slag pool greater than at the top of the furnace while maintaining the last named wall in slag tight contact with the floor.

11. A slag tap furnace, comprising, in combination, means for burning a slag producing fuel in the furnace, a floor constructed to sustain a pool of slag and including spaced cooling tubes, walls about the fioor and including spaced wall tubes, a fixed support, a rigid connection between the support and the floor and a part of one wall of the furnace at one position, secondary wall supports providing for movement of the other parts of that wall toward or away from said position, floor supports providing for movement of the floor toward or from said position, means connected to the floor tubes and contacting with another wall of the furnace to provide an increase or decrease in the cross section of the furnace near the slag pool greater than at the top of the furnace while maintaining the last named wall in slag tight contact with the floor.

12. A slag tap furnace comprising, in combination, a front wall including wall cooling tubes, 5 a burner secured at a position on that wall for burning a slag producing fuel in the furnace, a fixed support adjacent said position, a floor adapted to maintain a pool of slag in the furnace and including spaced floor cooling tubes, 10 a rigid connection between the support and said wall at one point adiacent said position, secondary wall supports on both sides of said connection, secondary floor supports, and other furnace walls including wall cooling tubes, and 15 means for pressing the walls into slag-tight engagement with the floor, the front wall and the floor being movable relative to the secondary supports.

13. A slag tap furnace, comprising, in combi- 20 nation, means for burning a slag producing fuel in the furnace, a floor constructed to sustain a pool of slag and including spaced cooling tubes, walls about the floor and including spaced wall tubes, a fixed support, rigid connection between 5 the support and the floor and a part of one wall of the furnace at one position, secondary wall supports providing for movement of the other parts of that wall toward or away from said position, fioor supports providing for movement 30 of the floor toward or from said position, means connected to the fioor tubes and contacting with another wall of the furnace to provide an increase or decrease in the cross section of the furnace near the slag pool greater than at the top 5 of the furnace while maintaining the last named wall in slag tight contact with the floor, and a guide device acting on two of said walls to maintain one edge of each against movement transversely of the plane of said one wall.

14.A slag tap-furnace, comprising, in combination, means for burning a slagproducing fuel in the furnace, a floor constructed to sustain a pool of slag and including spaced cooling tubes, walls about the floor and including spaced wall tubes, a fixed support, rigid connection between the support and the floor and one wall of the furnace at one position, secondary wall supports providing for movement of the parts of that wall remote from said connection toward or away from said position, floor supports providing for movement of the floor toward or from said position, and means connected to the fioor tubes and contacting with another wall of the furnace to provide an increase or decrease in the cross section of the furnace near the slag pool while maintaining the last named wall in slag tight contact with the fioor, said means including compression parts contacting with and acting upon the side walls at vertically spaced positions at appreci- 00 able distances above the slag pool.

15. A slag tap furnace comprising, in combination, a floor constructed to sustain a pool of slag and including spaced cooling tubes, walls including spaced cooling tubes and extending to positions below the floor level, buckstay elements movably supported exteriorly of the walls, compression members interposed between the buckstay elements and the walls, tension members connecting the fioor tubes and the buckstay elements whereby the latter force the compression members against the walls and the walls are pressed against the marginal portions of the fioor, a fixed support, a rigid connection between the support and one wall at one position along that "wall, and supports for other parts of the last mentioned wall and. the fioor providing for movement of these parts toward or from the position of said connection with the fixed support, this combination of elements vproviding for greater increases and decreases in the cross sectional area of that part of the furnace adjacent the slag pool than that part which is adjacent the top of the "furnace without impairing the maintenance of the slag pool.

16. A slag tap furnace comprising, in combination, a fioor constructed to sustain a pool of slag and including spaced cooling tubes, walls including spaced cooling tubes and extending to positions below the fioor level, force-transmitting members disposed exteriorly of the furnace walls, tension members respectively connecting the fioor with the force-transmitting members, compression members interposed respectively between the force-transmitting members and the furnace walls whereby the forces set up by the tension members will be transmitted to the walls through the compression members and the walls will be pressed against the marginal portions of the fioor, a fixed support, a rigid connection between the support and one wall at one position along that wall, and supports for other parts of the last mentioned wall and the fioor providing for movement of these parts toward or from the position of said connection with the fixed support.

17. In a slag tap furnace, the combination of upright fluid cooled walls defining a combustion chamber, a fluid cooled fioor extending transversely between the walls and constructed to sustain a pool of molten slag thereon, a rigid support, means adjacent the meeting edges of one upright walland the fioor for anchoring such wall and floor to the rigid support, and means for supporting the other walls and the remaining portions of the floor and providing for movement thereof incident to expansion and contraction and means providing a liquid tight connection between the marginal edges of the fioor and the upright walls.

18. In a slag tap furnace, the combination of upright fluid-cooled walls defining a combustion chamber, a. fluid-cooled floor extending transversely between the walls and constructed to sustain a pool of molten slag, a rigid support, means for anchoring one of the upright walls at a point adjacent the lower portion thereof to the rigid support, means connecting said one wall to the fioor, means for movably supporting the remaining portions of said one wall, the remaining upright walls and the floor to provide for the movement thereof relative to the point of anchorage due to expansion and contraction, and means providing for the maintenance of a liquid-tight connection between the upright walls and the fioor.

19. In a slag tap furnace, the combination of upright fluid-cooled walls defining a combustion chamber, a fluid-cooled fioor extending transversely between the upright walls and constructed to sustain a pool of molten slag, a rigid support, means for anchoring one of the upright walls and the floor at one point to the rigid support, means for movably supporting the remaining portion of said one wall, the floor, and the remaining upright walls to permit movement thereof relative to the point of anchorage due to expansion and contraction, and means connecting the fioor and walls to prevent the leakage of molten slag therebetween.

20. In a slag tap furnace, the combination of upright walls defining a combustion chamber and composed of upright tubes with closure means between the tubes, a fioor disposed transversely of the bottom of the combustion chamber and constructed to sustain a pool of molten slag, the fiooor comprising a row of spaced tubes and closure means betweer. the tubes, a header extending across the lower ends of the tubes forming one of the upright walls and common to both the tubes of said one wall and to the tubes of the fioor, means for rigidly anchoring the header at one point to a fixed support, and supporting means for the remaining portions of said header, said one furnace wall and the floor, and provid- 1 ing for movement thereof toward and away from the point of -anchorage to permit expansion and contraction.

21. In a furnace, the combination of upwardlyextending walls defining a combustion space. a boiler in communication with said space, a fioor extending transverselybeneath said space and constructed to sustain a pool of molten slag, each of said walls and the fioor comprising spaced cooling tubes having circulatory connections to the boiler and means for closing the spaces between tubes, means for positively connecting the peripheral edges of the 'fioor with the lower portions of the upwardly-extending walls so as to prevent the leakage of slag therebetween, and means for'supporting said walls and fioor in such a manner as to provide for movements thereof incident to expansion and contraction without impairing the aforesaid connecting means between the walls and floor.

22. In a furnace, the combination of upward-'- ly-extending walls defining a combustion space,

a boiler in communication with said space, a fioor extending transversely beneath said space and constructed to sustain a pool of molten slag, each 4 of said walls and the fioor comprising spaced cooling tubes having circulatory connections to the boiler and means for closing the spaces between tubes, means for positively connecting the peripheral edges of the fioor with the lower portions of the upwardly-extending walls so as to prevent the leakage of slag therebetween, and means for supporting said walls and floor and for preventing bodily displacement of the entire assembly while insuring freedom of expansion of the members locally in such a manner as not to impair the integrity of the structure or the tightness of the joints between the floor and walls.

23. In a furnace, the combination of means defining a combustion chamber including upwardly-extending walls and a floor, lateral stiffening and positioning means for at leastone of the walls and comprising a fixed abutment support restraining the stiffened wall against outward movement at points intermediate the heights thereof, and relatively stiff elongated members, each member being pivotally connected at one end to a support and extending downward along the lower portion of the stiffened wall and positively connected at its lower end to said one 05 wall 24. In a furnace, the combination of upwardly-extending walls defining a combustion space and comprising spaced cooling tubes; a bottom extendingtransversely beneath said space and 7 constructed to sustain a pool of molten slag resulting from the combustion of fuel in said space; and lateral stiffening and positioning means for at least one ofthe walls and comprising a fixed abutment support restrainingnthe stiffened wall 7 6 images:

against outward movement at points intermediate the height thereof, a plurality of upwardly-extending relatively stiff members disposed at the outside of the stiflened wall, means for pivotally connecting the upper ends of the still members to the abutment support so as to provide for movement of the lower portions of the members in directions toward and away from the stiflened walls, and means for positively connecting the 

